Gully Headcut Advance

Abstract

Gully headcut advance rates were examined in a cohesive soil with multiple overfall heights and discharges. Eleven tests were conducted in a 1.8-m-wide and 29-m-long flume at near field scale. Preformed overfalls with average heights of 0.96, 1.25, and 1.55 m were tested to failure at average discharges of 0.75, 1.59, and 2.42 m3/s. Soil from the same source was used for all tests. The observed headcut advance rates ranged from 0 to 1.6 m/h. All but one test displayed uniform headcut advance rates. The tests were performed while attempting to hold soil moisture and soil density constant and examining the influence of overfall height and discharge on headcut advance. The observed variation in placed soil conditions appeared to have as much influence on headcut advance as did the overfall height and discharge variations. Examination of a subset of the data suggests that the advance rate increases as the overfall height increases. The aeration status of the headcut and the dominant mode of failure are discussed.